Motor-control system



May 27, 1924. 1,495,787

0. LE G. FORTESCUE MOTOR CONTROL SYSTEM Filed Oct. 18. i920 INVENTOR E I Cbarleslefifbrtcscue ATTORNEY WITNESSES:

Patented May 1924.

UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESCUE, OI PITTSBURGH, PENNSYLVANIA, ASSTGNOR TO WEST- INGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF IPENN- BYLVANIA.

MOTOR-CONTROL SYSTEM.

To-all whom it may concern:

Be it known that I, Cnannns La G. Fon- TESCUE, a subject of the King of Great Brit;

ecglivalent to another portion ofthe resistor. T e contactor that maintains this portion of the resistor shunted is then closed.

ain, and a resident of Pittsburgh, in the For a better understanding of my inven- 6 county of Allegheny and State of Pennsylvania, have invented a new and-useful Improvement in Motor-Control Systems, of which the following is a specification.

My invention relates to motor-control systerns and it has articular relation to control systems whic require relatively large capacity resistors and which are employed where it is necessary to effect great economy in space, such, for example, as control systems employed to operate electric locomotives.

The object of my invention is to so construct and arrange a set of resistors in a motor-control s stem that a great saving in space will be e ected and that the resistors may be inserted in circuit or shunted to cause a gradual variation in resistance comparable to that which is attained when employing a liquid rheostat.

Heretofore, the type of liquid rheostat normally ada ted for railway service in some cases would gave been too large to be satisfactory. For that reason, grid resistors were employed.

Many ingenious schemes have been devised to efi'ect a very gradual change of resistance in cases where grid resistors of high capacity have been employed. These schemes usually depended upon a particu- 35. lar sequence of operation, especially the order in which contactors closed. Thus, the

disadvantages of highly complicated wiring systems employing a relatively large number of contactors have counterbalanced the ad- 40 vantages obtained through a relatively gradual change of resistance.

Briefly speaking, my invention consists in so employing resistors and contactors in conjunction with a liquid rheostat that a gradual change of resistance in circuit with a motor will be efiected. The liquid rheostat gradually shunts a portion of a resistor before the closure of a contactor that maints first position a. In this position, contact tains this ortion of the resistor shunted.

tion,' reference may be made to the accompanying drawmg- Figure 1 of which is a diagrammatic view of a motor-control system embodying my inventlon, and

Fig. 2 is a sequence chart showing the order in which the main contactors of the control system close. I

.lteferrmg to Fig. 1, a motor 1, having a primary winding 2 and a secondary winding '3, has its primary winding 2 connected to a source of electrical energy 4 by a circuitbreaker 5. A plurality of grid resistors 6 are connected in series relation with the secondary wmding 3 of the motor 1. A plural- 1ty of sets of contactors 11, 12 and 13 are employed for shunting the respective resistors 6. A master controller 14 controls the operation of the circuit-breaker 5, the sets of contactors 11, 12 and 13, and a contactor 15, which controls the energization of primary winding 16 of a torque motor 17. The torque motor 17 has a motor 18 mechanically connected to a shaft 19 which operates a li uid rheostat 20.

e liquid rheostat 20 comprises an arm 37, which is securely mounted upon the shaft- 19 and has movable contact members or plates 38 suspended therefrom, the stationary contact members or plates 39 and a tank containing electrolyte 40.

Dash-pot, time-element relays 22, 23 and 24 are employed to protect-the motor-control system from electrical overloads caused by too rapid operation of the master controller 14.

A plurality of three-pole contactors 25 and 26, which are mechanically connected to the relays 22 and 23, respectively, are adapted to electrically connect the liquid rheostat 20 to different portions of the resistors 6.

The operation of my control system is begun by actuating the master controller 14 to segment 27 engages a positively energized After the c osure of this contactor, the opercontact terminal 28 and also a contact teration of the liquid rheostat is repeated until minal 34, thereby establishing a circuit additional resistance has been gradually exthrough the actuating 0011 of the circuitcluded from circuit, by the liquid rheostat, breaker 5..

When the circuit-breaker 5 is thus closed, the primary winding 2 of the motor 1 is energized.

In the first position a; of the master controller 14, contact segment 27 also en gages contact terminal 35, thereby establishmg a circuit through the actuating coil of the con tactor 15, causing it to close.

When the contactor 15 is closed, the r 1- mary winding 16 of the torque motor 1 1s energized by a series transformer 36. The initial rushof current through the f rimary winding 2 of the motor 1 suflicient y energizes the series transformer 36 and the motor 17 electrically connected thereto to cause the rotor 18 to turn the arm 37, which is mounted upon the shaft 19, in such a manner as to separate the movable contact plates 38 of the liquid rheostat 20 from the stationary contact plates 39 thereof.

The resistors 6 are in series with the respective phase windings of the secondary winding 3 of the motor 1, and prevent a heavy rush of current through the windlng 3. The current in the primary winding 2 will radually decrease, thereby permittlng the p ates 38 to descend in the electrolyte 40 of the liquid rheostat 20 until the plates 38 engage the plates 39. The statlonary contact plates 39 are electr cally connected to portions 42 of phase reslstors 6 by conductors 41 and interlocks ll-out. Each of the conductors 41 is provided with an auxlhary switch or interlock ll-out, which is normally closed but assumes its open position upon the closure of the switch 11 to which it is mechanically connected. When the movable contact plates 38 engage the statlonary contact plates 39, portions 42 of the resistors 6 are completely shunted.

The master controller 14 may now be ac tuated to its second position b, in which position contact terminal 43 is engaged by contact segment 27, thereby energizing the actuating coil of the relay 22, which causes the relay 22 to close slowl The closure of the relay 22 permits the t ree-pole contactor 25 to close, thereby electrically connecting conductors 44 each having an interlock 12-out therein-to conductors 41 and thus to the contact plates 39 of the liquid rheostat 20.

An additional rush of current through the primary winding 2 of the motor 1 causes the torque motor 17 to elevate the contact plates 38 of the liquid rheostat 20, thereby inserting more resistance in series with the conducting members 39 and 41.

As the current falls in the primary winding 2 of the motor 1, the energization of the torque motor 17 is lessened and the plates 38 are again gradually lowered until they engage the contact terminals 39. In this way, a resistance, equal to mid-portions 45 of the resistors 6, may be gradually excluded from circuit. Prior, however, to this operation and simultaneously with the previously mentioned closure of the relay 22, the actuat ing coils of thecontactors 11 are energized through the contact member 46 of the relay 22, causing the contactors 11 to close and the auxiliary contactors or interlocks ll-out to assume their open position just before the torque motor 17 operates to raise the contact plates 38 of the li uid rheostat 20 and prior to the closure of t e three-pole contactor 25.

After the current in the rimary winding 2 of the motor 1 has diminished sufiiciently to permit the resistance of the electrolyte 40 of the liquid rheostat 20 to be excluded from circuit, contactors 12 may be closed by actuating the master controller 14 to its third position 0, thereby causing the contact se ment 27 to engage the contact terminal 4%. Under these conditions, since the rela 22 has assumed its closed position, a circuit is established through contact member 48 of the relay 22 to the actuating coil of the relay 23.

The actuating coil of the relay 23 being energized, the relay will slowly assume its closed position. WVhen the relay 23 is closed, a circuit is established, through the contact member 49 thereof and the contact member 46 of the relay 22, to the actuating coils of the contactors 12, thereby closing the contactors 12 and opening the auxiliary switches or interlocks 12-out.

The relay 23 having assumed its closed position, the three-pole contactor 26 is closed, thereby connecting the conductors 51 to the conductors 41, which are connected to the terminals 39 of the liquid rheostat 20.

The rush of current through the winding 2 of the motor 1 will again cause the torque motor 17 to raise the plates 38 of the liquid rheostat 20. After the current has fallen sufliciently in the primary winding 2 of the motor 1, the torque motor 17 will be sutficiently de-energized to permit the resistance of the electrolyte 40 to be gradually excluded from circuit and thus remove the last portions 52 of the resistors 6, and permit the closure of the contactors 13.

However, the contactors 13 will not be closed until after the dash-pot time-element relay 24 has assumed its closed position. This condition occurs after the contact members 46 and 49 of the relays 22 and 23, respectively, have completed a circuit comprising the actuating coil of the contactor 24.

Before the contactors 13 are closed, it is necessary for the master controller 14 to be the sets of contactors 11 may be closed only after the controller 14 has been actuated to its second position b, that contactors 12 can not be closed until the master controller 14: occupies its third position a and contactors 13 can not be closed until the master controller 14 has been moved to its fourth position (1.

If the master controller 14 is swung quickly over to its fourth position, the contactors 11, 12 and 13 will close in their usual sequence because of the operation of the timeelement relays 22, 23 and 24 and the motor will not be overloaded by the resistors 6 being shunted too rapidly.

While I have shown my invention in a preferred form, it is apparent that numerous modifications may be made in the apparatus employed and in the arrangements of switch sequence. For example, a difi'erent form of liquid rheostat may be employed in which the electrolyte 4O rapidly discharges upon closure of the contactors 11 and slowly returns to the tank before the contactors 12 are closed, this operation being repeated before closing the contactors 13.

It would also be possible to employ thermal relays instead of the dash-pot time-element relays that I have shown, and a differential-gear controller might be so designed as to effect substantially the same result. For these and other reasons, I desire that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. The combination with a resistor and means for succe$ively shunting portions of said resistor, of a liquid rheostat co-operating with said means for gradually varying the effective value of successive sections of said resistor 2. The combination with an electrical apparatus and a liquid rheostat for changing the values of the current traversing said apparatus, of means for maintaining said change in current after the operation of said liquid rheostat, said means being further capable of maintaining a second change in the current traversing said apparatus that is efiected by repeating the operation of said liquid rheostat.

3. The combination with a dynamo-electric machine and a resistor, of means for varying the current traversing said machine by shunting a portion of said resistor, and

a liquid rheostat for shunting a portion of said resistor prior to the operation of said means.

4. The combination with a dynamo-electric machine and a resistor connected thereto, of a plurality of contactors for shunting portions of said resistor, and a liquid rheostat for shunting a single portion of said resistor prior to the corresponding contactor closing.

5. In a motor-control system, the combination with a dynamo-electric machine, and a resistor connected thereto, of a plurality of contactors for shunting portions of said resistor in a predetermined sequence, a liquid rheostat capable of shunting a single portion of said resistor, and means for operating said rheostat and said contactors alternately to shunt said resistor.

6. In a motor-control system, the combination with a dynamo-electric machine, of a resistor connected thereto, a plurality of contactors for shunting said resistor, means for operating said contactors in a predetermined sequence, a liquid rheostat, means for con necting said rheostat to different portions of said resistor, and a torque motor for operatin said liquid rheostat.

In a motor-control system, the combination with a dynamo-electric machine, a resistor connected thereto, a plurality of contactors for shunting said resistors, a liquid rheostat, means for connecting said liquid rheostat to various parts of said resistor, a torque motor for automatically operating said liquid rheostat to shunt parts of said resistor, and a master controller for so operating said contactors and said means that said liquid rheostat shall be operated to shunt parts of said resistor prior to operation of the corresponding contactor.

8. The combination with a resistor, of means for gradually varying the effective value thereof comprising a liquid rheostat for gradually varying the effective value of successive sections of said resistor, and a plurality of switches for maintaining the successive effects of such liquid-rheostat operation. I

In testimony whereof, I have hereunto subscribed my name this 14th day of October 1920.

CHARLES LE G. FORTESCUE. 

